CN112117187A - Etching method and etching system - Google Patents
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- 238000001312 dry etching Methods 0.000 claims description 12
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 claims description 12
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/3065—Plasma etching; Reactive-ion etching
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
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Abstract
An etching method and an etching system are provided, the etching method is used for etching an etched layer by taking a covering layer as a mask, and the etching method comprises the following steps: obtaining the target thickness of the covering layer, wherein the target thickness is the etching thickness of the covered layer when the etching process etches the etched layer to the target depth; forming a mask layer with a target thickness on the etched layer, wherein part of the etched layer is exposed by the mask layer; and removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by using the etching process by taking the masking layer as a mask, and forming a target pattern in the etched layer. According to the embodiment of the invention, the masking layer with the target thickness is formed on the etched layer, and the target thickness is the etching thickness of the masked layer when the etched layer is etched to the target depth by the etching process, so that the etching depth of the etched layer can be accurately controlled, and the process window of the etching process can be increased.
Description
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to an etching method and an etching system.
Background
The etching technology is a technology for selectively corroding or stripping the surface of a semiconductor substrate or a surface covering film according to mask patterns or design requirements in a semiconductor process. Etching is a process of selectively removing unwanted material from the surface of an etched object (e.g., silicon) using chemical or physical methods, and is commonly performed using an etcher or the like. In a typical semiconductor process, an etching process is performed after a photolithography process, and a patterned photoresist layer is not significantly eroded by a corrosion source during the etching process, thereby completing a process step of pattern transfer.
The etching process is mainly divided into two types: dry etching and wet etching. The dry etching is to remove surface materials by means of physical or chemical reaction (or combination of physical and chemical reaction) between plasma gas and an etched piece; wet etching removes the surface material of the etched piece by chemical agents.
Disclosure of Invention
The invention provides an etching method and an etching system, which can enlarge a process window for etching an etched layer.
In order to solve the above problem, the present invention provides an etching method for etching an etched layer with a mask layer as a mask, the etching method comprising: obtaining the target thickness of the covering layer, wherein the target thickness is the etching thickness of the covered layer when the etching process etches the etched layer to the target depth; forming a mask layer with the target thickness on the etched layer, wherein part of the etched layer is exposed by the mask layer; and removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by using the etching process by taking the masking layer as a mask, and forming a target pattern in the etched layer.
Optionally, the etching process is an anisotropic etching process.
Optionally, the material of the etched layer comprises silicon or aluminum.
Optionally, the material of the masking layer includes silicon oxide or silicon nitride.
Optionally, the material of the etched layer is silicon, the etching process is a wet etching process, and an etching solution of the wet etching process is a KOH solution, a TMAH solution, or an HNA solution.
Optionally, the etching process is a wet etching process, and an etching selection ratio of the wet etching process to the etched layer and the masking layer is 100 to 1000.
Optionally, the etching process is a dry etching process, and an etching selection ratio of the dry etching process to the etched layer and the masking layer is 10 to 100.
Optionally, the step of forming a mask layer having a target thickness on the etched layer comprises: forming a masking material layer having a target thickness on the etched layer; forming a pattern layer with pattern openings on the covering material layer, wherein the pattern openings expose partial covering material layer; and removing the masking material layer exposed from the pattern opening by using the pattern layer as a mask, wherein the residual masking material layer is used as the masking layer.
Optionally, the target pattern is a groove.
Optionally, the step of obtaining a target thickness of the masking layer comprises: obtaining the etching selection ratio of the etching process to the etched layer and the covering layer; and obtaining the target thickness of the covering layer according to the etching selection ratio and the etching target depth.
Optionally, the step of obtaining the target thickness of the masking layer according to the etching selection ratio and the target depth of etching includes: and obtaining a ratio between the target depth and the etching selection ratio, wherein the ratio is used as the target thickness of the masking layer.
Optionally, the step of obtaining the etching selection ratio of the etching process to the etched layer and the masking layer includes: etching the etched layer by adopting the etching process, measuring the variation of the etching amount of the etched layer along with time, and obtaining a curve graph of the etching process to the variation of the etching rate of the etched layer along with time; etching the covering layer by adopting the etching process, measuring the variable quantity of the etching amount of the covering layer along with time, and obtaining a curve graph of the etching rate of the etching process to the covering layer along with the time; and obtaining the ratio between the etching rate of the etched layer and the etching rate of the covering layer according to the curve graph of the etching process to the etched layer along with the change of the etching rate of the etching process to the covering layer along with the change of the etching rate, wherein the ratio is used as the etching selection ratio.
Correspondingly, the invention also provides an etching system for etching the etched layer by using the covering layer as a mask, and the etching system comprises: the storage unit stores the etching selection ratio of the etching process to the etched layer and the covering layer; the calculating unit is used for obtaining the target thickness of the covering layer according to the etching selection ratio and the etching target depth; a growth unit for forming a mask layer having the target thickness on the etched layer, the mask layer exposing a portion of the etched layer; and the etching unit is used for removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by adopting the etching process, and forming a target pattern in the etched layer.
Optionally, the calculating unit is configured to obtain a ratio between the target depth and the etching selectivity, and the ratio is used as a target thickness of the masking layer.
Optionally, the storage unit includes: the first measuring unit is used for etching the etched layer by adopting the etching process, measuring the variable quantity of the etching quantity of the etched layer along with time, and obtaining a curve graph of the etching speed of the etching process to the etched layer along with the change of the time; the second measuring unit is used for etching the covering layer by adopting the etching process, measuring the variable quantity of the etching amount of the covering layer along with time, and obtaining a curve graph of the etching rate of the etching process to the covering layer along with the time; and the obtaining unit is used for obtaining the ratio between the etching rate of the etched layer and the etching rate of the covering layer according to a curve graph of the etching process to the etched layer along with the change of time and a curve graph of the etching process to the covering layer along with the change of time, and the ratio is used as the etching selection ratio.
Compared with the prior art, the technical scheme of the invention has the following advantages:
in the etching method of the embodiment of the invention, the target thickness of the covering layer is obtained, when the etching process etches the etched layer to the target depth, etching the masked layer to a thickness, and then forming a mask layer having a target thickness on the etched layer, the mask layer exposing a portion of the etched layer, and, therefore, in the process of removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by adopting the etching process, when the masking layer with the target thickness is removed, the etching thickness of the etched layer can easily reach the requirement of the target depth, thereby being beneficial to accurately controlling the etching depth of the etched layer, and the etching depth is limited by the process conditions of the etching process and the over-etching treatment is less limited, thereby being beneficial to improving the process stability of etching the etched layer and enlarging the process window of etching the etched layer.
Drawings
FIG. 1 is a flow chart corresponding to each step in an embodiment of an etching method of the present invention;
FIG. 2 is a flowchart illustrating steps corresponding to step S1 in FIG. 1;
FIG. 3 is a flowchart illustrating steps corresponding to step S11 in FIG. 2;
FIG. 4 is a graph of the etching process obtained in one embodiment of step S111 in FIG. 3 versus the etching rate of the etched layer as a function of time;
FIG. 5 is a graph of the etching rate of the etching process to the masking layer obtained in one embodiment of step S112 in FIG. 3 as a function of time;
FIG. 6 is a schematic structural diagram illustrating step S2 in FIG. 1 according to an embodiment;
FIG. 7 is a schematic structural diagram illustrating step S3 in FIG. 1 according to an embodiment;
FIG. 8 is a schematic diagram of an embodiment of an etching system according to the present invention.
Detailed Description
The current etching process is difficult to accurately control the etching depth of the etched layer, and the process window of the etching process is small. The following analysis is given by taking an etching process as a wet etching process as an example:
in a conventional wet etching process, the step of etching the etched layer generally includes: forming a masking layer on the etched layer, wherein part of the etched layer is exposed by the masking layer; and etching the etched layer with the exposed part of the thickness of the covering layer by taking the covering layer as a mask, and forming a target pattern in the etched layer.
However, the depth of etching using a wet etch process is typically limited by the Lifetime or effective time (Lifetime) of the etching solution. Specifically, the etching rate of the etched layer by the etching solution is gradually reduced as the etching time is increased. Therefore, in order to ensure that the etching solution has a high etching rate to the etched layer so that the etching depth meets the process requirement, the etching solution needs to be replaced at regular intervals.
On one hand, replacement of a new etching solution easily leads to an increase in process cost; on the other hand, the process of replacing the etching solution usually needs to take a certain time, and the etching process cannot be carried out in the process of replacing the etching solution, so that the production capacity is easily wasted; on the other hand, frequent replacement of the etching solution also tends to decrease the stability of the etching process, for example: the consistency of the etching depth is poor and the quality of the etching profile appearance is poor.
Another method is to add Over etching (Over etch) to the etched layer instead of replacing new etching solution, so as to make the actual etching depth reach the target depth.
However, since the etching rate of the etching solution to the etched layer gradually decreases with time, the difficulty of making the actual etching depth meet the requirement of the target depth by increasing the over-etching manner to the etched layer is large, and it is difficult to accurately control the etching depth. Moreover, in the conventional wet etching process, the masking layer usually adopts photoresist, the etching solution hardly etches the masking layer or the etching rate of the masking layer is very low, and after the etching is finished, the residual masking layer is removed by the photoresist removing process. And because the wet etching process also has the characteristic of isotropic etching, increasing the over-etching of the etched layer easily causes more lateral etching of the etched layer at the bottom of the edge position of the covering layer, so that undercutting or lateral erosion (underrout) is easy to occur, and the quality of the etched profile appearance is poor.
In order to solve the technical problem, the invention provides an etching method and an etching system, wherein the etching method is used for etching an etched layer by taking a covering layer as a mask, and comprises the following steps: obtaining the target thickness of the covering layer, wherein the target thickness is the etching thickness of the covered layer when the etching process etches the etched layer to the target depth; forming a mask layer with the target thickness on the etched layer, wherein part of the etched layer is exposed by the mask layer; and removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by using the etching process by taking the masking layer as a mask, and forming a target pattern in the etched layer.
In the etching method of the embodiment of the invention, the target thickness of the covering layer is obtained, when the etching process etches the etched layer to the target depth, etching the masked layer to a thickness, and then forming a mask layer having a target thickness on the etched layer, the mask layer exposing a portion of the etched layer, and, therefore, in the process of removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by adopting the etching process, when the masking layer with the target thickness is removed, the etching thickness of the etched layer can easily reach the requirement of the target depth, thereby being beneficial to accurately controlling the etching depth of the etched layer, and the etching depth is limited by the process conditions of the etching process and the over-etching treatment is less limited, thereby being beneficial to improving the stability of the process for etching the etched layer and increasing the process window for etching the etched layer.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
FIG. 1 is a flow chart corresponding to each step in an embodiment of the etching method of the present invention. The etching method of the embodiment is used for etching the etched layer by taking the covering layer as a mask.
Referring to fig. 1, step S1 is executed to obtain a target thickness of the masking layer, where the target thickness is an etching thickness of the masked layer when the etching process etches the etched layer to a target depth.
By obtaining a target thickness for the masking layer, provision is made for subsequent formation of a masking layer having the target thickness over the etched layer.
In this embodiment, the target thickness is an etching thickness of the masked layer when the etched layer is etched to a target depth by an etching process, so that in a subsequent process of removing the masking layer and the etched layer with a partial thickness exposed by the masking layer by the etching process, the etching thickness of the etched layer is easy to meet the requirement of the target depth when the masking layer with the target thickness is removed, thereby facilitating accurate control of the etching depth of the etched layer.
Referring to fig. 2 in combination, a flowchart corresponding to each step in the embodiment of step S1 in fig. 1 is shown, and the step of obtaining the target thickness of the mask layer includes:
step S11 is executed to obtain the etching selection ratio of the etching process to the etched layer and the mask layer.
By obtaining the etching selection ratio of the etching process to the etched layer and the covering layer, the target thickness of the covering layer can be obtained according to the etching selection ratio and the target depth of etching.
In the embodiment, the etching process has an etching selection ratio for the etched layer and the masking layer, and in the field of semiconductors, the etching selection ratio for the etched layer and the masking layer in the etching process does not change with time, so that after the etching selection ratio is obtained, the target thickness of the masking layer can be obtained according to the etching selection ratio and the etching target depth, and the accuracy and the efficiency of the obtained target thickness of the masking layer can be improved.
The etched layer is a material layer to be etched by an etching process to form a target pattern.
The etched layer may be a substrate or a film layer formed on the substrate, for example: dielectric layers, metal layers, and the like. In this embodiment, the etched layer is a silicon substrate.
In this embodiment, the material of the etched layer is silicon. In other embodiments, the material of the etched layer may also be other materials, depending on the actual process and the function of the etched layer, such as: aluminum.
The mask layer is used as a mask for etching the etched layer to form a target pattern.
It should be noted that the material of the masking layer is different from the material of the etched layer, so that the etching process can have different etching rates for the masking layer and the etched layer, and the etching rate for the masking layer is smaller than that for the etched layer.
In this embodiment, the etched layer is made of silicon, and the masking layer may be made of silicon oxide or silicon nitride. The silicon oxide and the silicon nitride are common materials in the semiconductor process, so that the process compatibility is improved, the process cost is reduced, the silicon oxide or the silicon nitride is selected, the etching process can simultaneously etch the covering layer and the etched layer, and the etching rate of the etching process to the covering layer is smaller.
Specifically, the material of the masking layer is silicon oxide.
In other embodiments, when the material of the etched layer is other materials, a suitable material is selected as the mask layer. For example: when the material of the etched layer is aluminum, the material of the masking layer can be silicon nitride.
In this embodiment, the etching process is an anisotropic etching process. And subsequently, removing the etched layer with the exposed part of the thickness of the masking layer, forming a target pattern in the etched layer, and facilitating the improvement of the profile appearance quality of the target pattern by selecting an anisotropic etching process.
In this embodiment, the etching process is a wet etching process. The wet etching process is simple to operate and low in process cost.
The etching selection ratio of the wet etching process to the etched layer and the covering layer is not too small or too large. If the etching selection ratio of the wet process to the etched layer and the masking layer is too small, the etching rate of the masking layer is higher when the etched layer with a part of thickness is removed, the required thickness of the masking layer is too large, more time is needed for forming the masking layer and removing the masking layer, and the production capacity is easily reduced; if the etching selection ratio of the wet etching process to the etched layer and the masking layer is too large, in the process of etching the etched layer, the etching rate of the wet etching process to the masking layer is too slow, which easily causes a high probability of undercut (undercut) in the etched layer, or the etched layer is easily split or peeled off. For this reason, in this embodiment, the etching selection ratio of the wet etching process to the etched layer and the masking layer is 100 to 1000, for example: 200, 300, 450, 600, 800, etc.
In this embodiment, the material of the etched layer is silicon, the etching solution of the wet etching process includes a KOH solution, and the KOH solution is an etching solution commonly used for etching silicon in a semiconductor process, which is beneficial to improving process compatibility.
In other embodiments, the etching solution of the wet etching process may also be other suitable solutions for etching silicon, such as: TMAH (tetramethylammonium hydroxide) solution, HNA solution, and the like. Wherein, the HNA solution refers to a mixed solution of hydrofluoric acid, nitric acid and acetic acid.
In other embodiments, when the material of the etched layer is other materials, a suitable etching solution is selected to perform the wet etching process. For example: when the material of the layer to be etched is aluminum, the wet etching process may be performed using M2 (aluminum etchant). Wherein, the M2 solution is a mixed solution of phosphoric acid, nitric acid and acetic acid.
In still other embodiments, the etching process may also be a dry etching process according to actual process requirements. In this embodiment, in order to achieve better process stability, reduce process difficulty, and improve production throughput, the etching selection ratio of the dry etching process to the etched layer and the masking layer is 10 to 100, for example: 50, 75, 90, etc.
Referring to fig. 3 in combination, which shows a flowchart corresponding to each step in the embodiment of step S11 in fig. 2, the step of obtaining the etching selection ratio of the etching process to the etched layer and the masking layer includes:
and S111 is executed, the etching process is adopted to etch the etched layer, the variation of the etching amount of the etched layer along with time is measured, and a curve graph of the etching process to the variation of the etching rate of the etched layer along with time is obtained.
And obtaining a curve graph of the etching process to the change of the etching rate of the etched layer along with time so as to prepare for obtaining the ratio of the etching rate of the etched layer to the etching rate of the covering layer subsequently.
Specifically, the etching amount of the etching process to the etched layer in different time is collected, then the etching rate of the etching process to the etched layer in different time is obtained according to the etching amount and the corresponding etching time, and then a curve graph of the etching rate of the etching process to the etched layer changing with time is fitted according to the etching rate of the etching process to the etched layer in different time.
Referring to fig. 4 in combination, a graph of the etching process obtained in one embodiment of step S111 in fig. 3 versus the etching rate of the etched layer with time is shown.
Specifically, in this embodiment, the etching process is a wet etching process, and the etching solution of the wet etching process is a KOH solution, so that a graph of the change of the etching rate of the KOH solution to silicon with time is obtained, where an abscissa of the graph is time (unit: day), and an ordinate of the graph is the etching rate of the KOH solution to silicon (unit:
)。
as can be seen from fig. 4, the etching rate of the KOH solution to silicon gradually decreases with time.
And S112, etching the covering layer by adopting the etching process, measuring the variation of the etching amount of the covering layer along with time, and obtaining a curve graph of the etching rate of the covering layer along with the time variation of the etching process.
And preparing for obtaining the ratio of the etching rate of the etched layer to the etching rate of the covering layer in the follow-up process by obtaining a curve graph of the etching rate of the etching process to the covering layer along with the change of time.
Specifically, the etching amount of the etching process to the covering layer in different time is collected, then the etching rate of the etching process to the covering layer in different time is obtained through the etching amount and the corresponding etching time, and then a curve graph of the etching rate of the etching process to the covering layer along with the change of time is fitted according to the etching rate of the etching process to the covering layer in different time.
It should be noted that, when the etching process is used for the masking layer and the etching process is used for the etched layer, the process parameters or process conditions of the etching process are the same, so as to ensure the effectiveness of the obtained curve graphs of the etching rate of the etching process for the etched layer and the etching process for the masking layer changing with time, and further ensure the effectiveness of the subsequently obtained etching selection ratio data of the etching process for the etched layer and the masking layer.
In this embodiment, the etching process is a wet etching process, and therefore, when the etching process is used to etch the masking layer, the process parameters (e.g., concentration of etching solution, temperature, etc.) of the wet etching process are the same as the process parameters for etching the etched layer.
Referring to fig. 5 in combination, a graph of the etching rate of the etching process to the masking layer obtained in the embodiment of step S112 in fig. 3 with time is shown.
Specifically, in this embodiment, the etching process is a wet etching process, and the etching solution of the wet etching process is a KOH solution, so that a graph of the change of the etching rate of the KOH solution to the silicon oxide with time is obtained, where the abscissa of the graph is time (unit: day), and the ordinate is the etching rate of the KOH solution to the silicon oxide (unit:
)。
as can be seen from fig. 5, the etching rate of the KOH solution to silicon gradually decreases with time.
In this embodiment, the etching process is a wet etching process, and the etching rates of the etching solution to the etched layer and the masking layer are both gradually decreased with time, so that when a time-varying graph of the etching rate of the etching process to the etched layer and a time-varying graph of the etching rate of the etching process to the masking layer are obtained, the life or the effective time of the etching solution needs to be considered, that is, when the life or the effective time of the etching solution is reached, the collection of the etching rate of the etching solution to the etched layer and the masking layer can be stopped.
In the present embodiment, a graph of the etching rate of the etching solution to the etched layer over time within 6 days and a graph of the etching rate of the etching solution to the masking layer over time are taken as examples. In other embodiments, graphs of etch rate versus time for other times may also be collected, depending on the actual process.
And step S113 is executed to obtain a ratio between the etching rate of the layer to be etched and the etching rate of the cap layer according to a time-varying graph of the etching rate of the etching process to the layer to be etched and a time-varying graph of the etching rate of the etching process to the cap layer, where the ratio is used as the etching selection ratio.
As can be seen from fig. 4 and 5, although the etching rates of the etching process to the etched layer and the masking layer are gradually decreased with time, the ratio between the etching rate of the etching process to the etched layer and the etching rate of the masking layer is substantially constant, that is, the etching selectivity of the etching process to the etched layer and the masking layer is constant, so that the target thickness of the masking layer can be obtained according to the etching selectivity and the target depth of etching, and the actual etching depth meets the requirement of the target depth.
Specifically, a graph of the change of the etching rate of the etching process to the etched layer along with time and a graph of the change of the etching rate of the etching process to the covering layer along with time are placed in the same coordinate system, then ratios of corresponding etching rates of a plurality of groups of etched layers at different time points to corresponding etching rates of the covering layer are obtained, and then an average value of the ratios of the etching rates of the plurality of groups is obtained, wherein the average value of the ratios of the etching rates of the plurality of groups is used as an etching selection ratio of the etching process to the etched layer and the covering layer.
It should be further noted that, in this embodiment, at least the ratio of the corresponding etching rate of the etched layer to the corresponding etching rate of the masking layer at 20 sets of time points is obtained, so that the deviation or the error of the etching selection ratio value is favorably reduced, and the subsequent etching precision of the etched layer is favorably improved.
From the data in fig. 4 and 5, the etching selectivity of the KOH solution to silicon and silicon oxide is 300, that is, the etching selectivity of the etching process to the etched layer and the mask layer is 300 in this embodiment.
It should be noted that, according to the actual process, when the process conditions of the etching process are changed, for example: when the concentration or the temperature of the etching solution changes, the etching selection ratio of the etching to the etched layer and the covering layer by adopting the same etching process is still a fixed value along with the change of time, and the etching selection ratio can also be other values.
With continued reference to fig. 2, the step of obtaining a target thickness of the masking layer further comprises: and step S2 is executed, and the target thickness of the masking layer is obtained according to the etching selection ratio and the target depth of etching.
Obtaining a target thickness of the masking layer in preparation for a subsequent formation of the masking layer having the target thickness on the etched layer.
Specifically, the step of obtaining the target thickness of the masking layer according to the etching selection ratio and the target depth of etching comprises: and obtaining a ratio between the target depth and the etching selection ratio, wherein the ratio is used as the target thickness of the masking layer.
For example: in this embodiment, the etching selection ratio is 300, and the target depth of the etching is 90 μm, so that the target thickness of the masking layer is 0.3 μm (90 μm/300).
It should be noted that, in this embodiment, an example is described in which an etching selection ratio of the etching process to the etched layer and the masking layer is obtained, and then a target thickness of the masking layer is obtained according to the etching selection ratio and the target depth of etching.
In other embodiments, according to the actual process, a plurality of sets of tests or tests may be performed to obtain a plurality of sets of etching thicknesses of the corresponding masking layer as the target thicknesses when the etching process etches the etched layer to the target depth.
In other embodiments, the target thickness of the masking layer may also be obtained by other suitable means.
Referring to fig. 1 and 6 in combination, fig. 6 is a schematic structural diagram corresponding to an embodiment of step S2 in fig. 1, and step S2 is performed to form a masking layer 110 with the target thickness on the etched layer 100, where the masking layer 110 exposes a portion of the etched layer 100.
The masking layer 110 is used as a mask for subsequent etching of the etched layer 100.
By forming the masking layer 110 with the target thickness, after the masking layer 110 and the etched layer 100 with the exposed partial thickness of the masking layer 110 are removed by the etching process, the etching depth of the etched layer 100 can reach the target depth requirement.
In this embodiment, the step of forming the masking layer 110 includes: forming a masking material layer (not shown) having the target thickness on the etched layer 100; forming a pattern layer with pattern openings on the covering material layer, wherein the pattern openings expose partial covering material layer; and removing the masking material layer exposed from the pattern openings by using the pattern layer as a mask, wherein the remaining masking material layer is used as the masking layer 110.
The masking material layer is used to form the masking layer 110.
Specifically, the process of forming the masking material layer may be a Plasma Enhanced Chemical Vapor Deposition (PECVD) process, a thermal oxidation growth process, or the like.
The pattern layer is used as a mask for etching the covering material layer to form a covering layer.
The material of the pattern layer may be photoresist.
In this embodiment, the masking material layer exposed by the pattern opening is removed by an anisotropic dry etching process. The anisotropic dry etching process has the characteristic of anisotropic etching, is favorable for improving the controllability of an etched section, has high etching precision and is favorable for reducing the damage to an etched layer when the masking material layer exposed out of the pattern opening is removed.
In other embodiments, a wet etching process may be further used to remove the masking material layer exposed by the pattern opening according to actual process requirements. The wet etching is easy to realize larger etching selection ratio and is also beneficial to preventing the etched layer from being damaged.
In other embodiments, according to the actual process, the masking material layer exposed by the pattern opening may be etched by an anisotropic dry etching process, and then the remaining masking material layer exposed by the pattern opening may be removed by a wet etching process, which is also beneficial to reducing the damage to the etched layer.
And removing the pattern layer after removing the covering material layer exposed from the pattern opening. Specifically, the pattern layer may be removed using an ashing process.
Referring to fig. 1 and 7 in combination, fig. 7 is a schematic structural diagram corresponding to an embodiment of step S3 in fig. 1, and step S3 is executed to remove the masking layer 110 and the etched layer 100 with a partial thickness exposed by the masking layer 110 by using the etching process, and form a target pattern in the etched layer 100.
In this embodiment, the target thickness of the masking layer is obtained first, and when the etching process etches the etched layer to the target depth, the mask layer is etched to a thickness, and then a mask layer 110 having the target thickness is formed on the etched layer, and thus, in the process of removing the masking layer 110 and the etched layer 100 with the exposed thickness of the masking layer 110 by the etching process, when the masking layer 110 with the target thickness is removed, the etching thickness of the etched layer 100 can easily reach the target depth, thereby being beneficial to accurately controlling the etching depth of the etched layer 100, and the etching depth is limited by the process conditions of the etching process and the over-etching treatment is less limited, which is beneficial to improving the process stability of etching the etched layer 100 and increasing the process window of etching the etched layer 100.
Specifically, the etching process has an etching selection ratio for the etched layer 100 and the masking layer 110, and the etching selection ratio for the etched layer 100 and the masking layer 110 in the etching process does not generally change with time, and in this embodiment, the target thickness of the masking layer is obtained according to the etching selection ratio and the target depth of etching, which is beneficial to improving the accuracy and efficiency of the obtained target thickness of the masking layer, so that after the masking layer 110 with the target thickness is formed on the etched layer 100, the difficulty of making the etching thickness of the etched layer 100 reach the target depth is further reduced, thereby further accurately controlling the etching depth of the etched layer 100 and increasing the process window for etching the etched layer 100.
In this embodiment, when the etching process is used to remove the etched layer with a partial thickness exposed by the masking layer 110, and a target pattern is formed in the etched layer, the masking layer 110 is also completely removed.
In this embodiment, the target pattern is a groove 200, and the depth of the groove 200 is favorable for being accurately controlled.
In particular, in the embodiment, the etching process is a wet etching process, and by obtaining the target thickness of the masking layer 110 and forming the masking layer 110 with the target thickness, it is beneficial to reduce the limitation of the depth of the groove 200 by the life (Lifetime) of the etching solution, the process window for forming the groove 200 is large, and the etching solution does not need to be replaced at regular time, which is beneficial to reducing the process cost, improving the production capacity, and also beneficial to improving the consistency of the etching depth.
Moreover, excessive etching of the etched layer 100 is not required to be additionally added, which is beneficial to preventing the problem of lateral etching, and further beneficial to preventing the problem of Undercut or lateral erosion (underrout), thereby improving the profile appearance quality of the groove 200.
It should be noted that, in this embodiment, since the etching depth of the etched layer 100 also reaches the target depth when the masking layer 110 with the target thickness is removed, even if the masking layer 110 is completely removed, the etched layer 100 is etched, and since there is no masking layer on the etched layer 100 at this time, the etching process can simultaneously etch the etched layer 100 at the bottom of the groove 200 and the etched layer 100 exposed from the groove 200, the difference between the etching amounts of the etched layer 100 at the bottom of the groove 200 and the etched layer 100 exposed from the groove 200 is small, the depth variation of the groove 200 is small, the target depth requirement can still be met, and accordingly, it is beneficial to increase the process window for etching the etched layer 100 to form the groove 200 with the target depth.
Correspondingly, the invention also provides an etching system which is used for etching the etched layer by taking the covering layer as a mask. Referring to FIG. 8, a schematic diagram of an embodiment of an etching system of the present invention is shown.
The etching system comprises: the storage unit stores the etching selection ratio of the etching process to the etched layer and the covering layer; the calculating unit is used for obtaining the target thickness of the covering layer according to the etching selection ratio and the etching target depth; a growth unit for forming a mask layer having the target thickness on the etched layer, the mask layer exposing a portion of the etched layer; and the etching unit is used for removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by adopting the etching process, and forming a target pattern in the etched layer.
The storage unit stores the etching selection ratio of the etching process to the etched layer and the covering layer, and in the semiconductor field, the etching selection ratio of the etching process to the etched layer and the covering layer does not change with time generally, so that the calculation unit can obtain the target thickness of the covering layer according to the etching selection ratio and the etching target depth, the growth unit is used for forming the covering layer with the target thickness on the etched layer, therefore, in the process that the etching unit adopts the etching process to remove the covering layer and the etched layer with the exposed part of the thickness of the covering layer, when the covering layer with the target thickness is removed, the etching thickness of the etched layer can easily reach the requirement of the target depth, thereby being beneficial to accurately controlling the etching depth of the etched layer, and the etching depth is limited by the process conditions of the etching process and the over-etching treatment, the method is favorable for improving the stability of the process for etching the etched layer and increasing the process window for etching the etched layer.
The storage unit stores the etching selection ratio of the etching process to the etched layer and the covering layer, so that the calculating unit can obtain the target thickness of the covering layer according to the etching selection ratio and the etching target depth.
The etched layer is a material layer to be etched by an etching process to form a target pattern.
The etched layer may be a substrate or a film layer formed on the substrate, for example: dielectric layers, metal layers, and the like. In this embodiment, the etched layer is a silicon substrate.
In this embodiment, the material of the etched layer is silicon. In other embodiments, the material of the etched layer may also be other materials, depending on the actual process and the function of the etched layer, such as: aluminum.
The masking layer is used as a mask for etching the etched layer to form the target pattern.
It should be noted that the material of the masking layer is different from the material of the etched layer, so that the etching process can have different etching rates for the masking layer and the etched layer, and the etching rate for the masking layer is smaller than that for the etched layer.
In this embodiment, the etched layer is made of silicon, and the masking layer may be made of silicon oxide or silicon nitride. The silicon oxide and the silicon nitride are common materials in the semiconductor process, so that the process compatibility is improved, the process cost is reduced, the silicon oxide or the silicon nitride is selected, the etching process can simultaneously etch the covering layer and the etched layer, and the etching rate of the etching process to the covering layer is smaller.
Specifically, the material of the masking layer is silicon oxide.
In other embodiments, when the material of the etched layer is other materials, a suitable material is selected as the mask layer. For example: when the material of the etched layer is aluminum, the material of the masking layer can be silicon nitride.
The memory cell includes: the first measuring unit is used for etching the etched layer by adopting the etching process, measuring the variation of the etching amount of the etched layer along with time, and obtaining a curve graph of the etching rate of the etching process to the etched layer along with the time variation.
The first measuring unit is used for preparing for obtaining the etching selection ratio of the etched layer and the covering layer.
The first measuring unit obtains a curve graph of the etching process to the etching rate of the etched layer along with the change of time, and prepares for obtaining the ratio of the etching rate of the etched layer to the etching rate of the covering layer.
Specifically, the first measuring unit collects the etching amount of the etching process to the etched layer in different time, then obtains the etching rate of the etching process to the etched layer in different time according to the etching amount and the corresponding etching time, and fits a curve graph of the etching rate of the etching process to the etched layer changing with time according to the etching rate of the etching process to the etched layer in different time.
The memory cell further includes: and the second measuring unit is used for etching the covering layer by adopting the etching process, measuring the variable quantity of the covering layer along with time and obtaining a curve graph of the etching rate of the etching process to the covering layer along with the time.
The second measurement unit provides for obtaining an etch selectivity ratio of the etched layer and the masking layer.
Specifically, the second measuring unit collects the etching amount of the etching process to the covering layer in different time, then obtains the etching rate of the etching process to the covering layer in different time according to the etching amount and the corresponding etching time, and fits a curve graph of the etching rate of the etching process to the covering layer along with the change of the etching.
The memory cell further includes: and the obtaining unit is used for obtaining the ratio between the etching rate of the etched layer and the etching rate of the covering layer according to a curve graph of the etching process to the etched layer along with the change of time and a curve graph of the etching process to the covering layer along with the change of time, and the ratio is used as the etching selection ratio.
Although the etching rate of the etching process to the etched layer and the masking layer is gradually reduced along with the time change, the ratio of the etching rate of the etching process to the etched layer to the etching rate of the masking layer is basically kept unchanged, that is, the etching selection ratio of the etching process to the etched layer and the masking layer is a fixed value, so that the subsequent calculation unit can obtain the target thickness of the masking layer according to the etching selection ratio and the target depth of etching, and the actual etching depth meets the requirement of the target depth.
Specifically, the obtaining unit places a time-varying graph of the etching rate of the etching process on the layer to be etched and a time-varying graph of the etching rate of the etching process on the covering layer in the same coordinate system, obtains ratios of corresponding etching rates of the groups of layers to be etched at different time points to corresponding etching rates of the covering layer, and obtains an average value of the ratios of the groups of etching rates, wherein the average value of the ratios of the groups of etching rates is used as an etching selection ratio of the etching process on the layer to be etched and the covering layer.
The calculation unit obtains a target thickness of the masking layer, and outputs a value of the target thickness to the growth unit, thereby forming the masking layer having the target thickness.
Specifically, the method is used for obtaining a ratio between the target depth and the etching selectivity, and the ratio is used as a target thickness of the masking layer.
The growth unit is used for forming a covering layer with the target thickness and preparing for the etching unit to etch the etched layer.
The masking layer is used as a mask for subsequent etching of the etched layer.
The growth unit forms a covering layer with the target thickness, so that after the etching unit removes the covering layer and the etched layer with the exposed part of the thickness of the covering layer by adopting the etching process, the etching depth of the etched layer can reach the requirement of the target depth.
The etching unit is used for etching the etched layer, so that a target pattern is formed in the etched layer.
The etching process has etching selection ratio to the etched layer and the covering layer, and the etching selection ratio of the etching process to the etched layer and the covering layer does not change with time generally, so that in the process of removing the covering layer and the exposed part of the etched layer with the thickness of the covering layer by the etching unit through the etching process, when the covering layer with the target thickness is removed, the etching thickness of the etched layer is easy to meet the requirement of the target depth, the etching depth of the etched layer is favorably and accurately controlled, the etching depth is limited by the process conditions of the etching process and the over-etching treatment, the stability of the process for etching the etched layer is favorably improved, and the process window for etching the etched layer is favorably increased.
In this embodiment, the etching unit is an anisotropic etching unit. And the anisotropic etching unit is selected, so that the profile appearance quality of the target graph is improved.
In this embodiment, the target pattern is a groove, and the depth of the groove is favorable for being accurately controlled.
In this embodiment, the etching unit is a wet etching unit. That is, the etching process is a wet etching process. The etching solution of the wet etching process comprises a KOH solution. The wet etching process is simple to operate and low in process cost, the KOH solution is an etching solution commonly used for etching silicon in a semiconductor process, the process compatibility is favorably improved, and in addition, the KOH solution is an alkaline chemical etching solution and can realize anisotropic etching on the silicon.
In other embodiments, the etching solution of the wet etching process may also be other suitable solutions for etching silicon, such as: TMAH (tetramethylammonium hydroxide) solution, HNA solution, and the like. Wherein, the HNA solution refers to a mixed solution of hydrofluoric acid, nitric acid and acetic acid.
In other embodiments, when the material of the etched layer is other materials, a suitable etching solution is selected to perform the wet etching process. For example: when the material of the layer to be etched is aluminum, the wet etching process may be performed using M2 (aluminum etchant). Wherein, the M2 solution is a mixed solution of phosphoric acid, nitric acid and acetic acid.
In still other embodiments, the etching process may also be a dry etching process according to actual process requirements.
In this embodiment, the etching process is a wet etching process, and the target thickness of the masking layer is calculated in advance and the masking layer 110 having the target thickness is formed, so that the depth of the groove 200 is favorably reduced and limited by the life (Lifetime) of the etching solution, and the process window for forming the groove 2000 is large, and a new etching solution does not need to be replaced at regular time, thereby being favorable for reducing the process cost, improving the production capacity, and also being favorable for improving the uniformity of the etching depth.
Moreover, over-etching of the etched layer is not required to be additionally increased, and the problem of transverse etching is favorably prevented, so that the problem of Undercut or lateral erosion (underrout) is favorably prevented, and the profile appearance quality of the groove 200 is improved.
It should be noted that, in this embodiment, since the etching depth of the etched layer 100 also reaches the target depth when the masking layer 110 with the target thickness is removed, even if the etched layer 100 is etched after the masking layer 110 is completely removed, since there is no masking layer on the etched layer 100 at this time, the etching process can simultaneously etch the etched layer 100 at the bottom of the groove 200 and the etched layer 100 exposed from the groove 200, the difference between the etching amounts of the etched layer 100 at the bottom of the groove 200 and the etched layer 100 exposed from the groove 200 is small, the depth change of the groove 200 is small, and the target depth requirement can still be met.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (15)
1. An etching method is used for etching a layer to be etched by taking a masking layer as a mask, and is characterized by comprising the following steps of:
obtaining the target thickness of the covering layer, wherein the target thickness is the etching thickness of the covered layer when the etching process etches the etched layer to the target depth;
forming a mask layer with the target thickness on the etched layer, wherein part of the etched layer is exposed by the mask layer;
and removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by using the etching process by taking the masking layer as a mask, and forming a target pattern in the etched layer.
2. The etching method of claim 1, wherein the etching process is an anisotropic etching process.
3. The etching method according to claim 1, wherein a material of the layer to be etched includes silicon or aluminum.
4. The etching method according to claim 1, wherein a material of the masking layer comprises silicon oxide or silicon nitride.
5. The etching method according to claim 1, wherein the material of the layer to be etched is silicon, the etching process is a wet etching process, and an etching solution of the wet etching process is a KOH solution, a TMAH solution or an HNA solution.
6. The etching method according to claim 1, wherein the etching process is a wet etching process, and an etching selection ratio of the wet etching process to the etched layer and the masking layer is 100 to 1000.
7. The etching method according to claim 1, wherein the etching process is a dry etching process, and an etching selection ratio of the dry etching process to the etched layer and the masking layer is 10 to 100.
8. The etching method according to claim 1, wherein the step of forming a mask layer having a target thickness on the layer to be etched comprises: forming a masking material layer having a target thickness on the etched layer;
forming a pattern layer with pattern openings on the covering material layer, wherein the pattern openings expose partial covering material layer;
and removing the masking material layer exposed from the pattern opening by using the pattern layer as a mask, wherein the residual masking material layer is used as the masking layer.
9. The etching method according to claim 1, wherein the target pattern is a groove.
10. The etching method of claim 1, wherein obtaining a target thickness of the masking layer comprises: obtaining the etching selection ratio of the etching process to the etched layer and the covering layer;
and obtaining the target thickness of the covering layer according to the etching selection ratio and the etching target depth.
11. The etching method of claim 10, wherein obtaining a target thickness of the masking layer based on the etch selectivity and the target depth of the etch comprises: and obtaining a ratio between the target depth and the etching selection ratio, wherein the ratio is used as the target thickness of the masking layer.
12. The etching method according to claim 10, wherein the step of obtaining an etching selection ratio of the etching process to the etched layer and the mask layer comprises: etching the etched layer by adopting the etching process, measuring the variation of the etching amount of the etched layer along with time, and obtaining a curve graph of the etching process to the variation of the etching rate of the etched layer along with time;
etching the covering layer by adopting the etching process, measuring the variable quantity of the etching amount of the covering layer along with time, and obtaining a curve graph of the etching rate of the etching process to the covering layer along with the time;
and obtaining the ratio between the etching rate of the etched layer and the etching rate of the covering layer according to the curve graph of the etching process to the etched layer along with the change of the etching rate of the etching process to the covering layer along with the change of the etching rate, wherein the ratio is used as the etching selection ratio.
13. An etching system for etching a layer to be etched by using a mask layer as a mask, comprising:
the storage unit stores the etching selection ratio of the etching process to the etched layer and the covering layer;
the calculating unit is used for obtaining the target thickness of the covering layer according to the etching selection ratio and the etching target depth;
a growth unit for forming a mask layer having the target thickness on the etched layer, the mask layer exposing a portion of the etched layer;
and the etching unit is used for removing the masking layer and the etched layer with the exposed part of the thickness of the masking layer by adopting the etching process, and forming a target pattern in the etched layer.
14. The etching system of claim 13, wherein the calculation unit is configured to obtain a ratio between the target depth and the etch selectivity as the target thickness of the masking layer.
15. The etching system of claim 13, wherein the storage unit comprises: the first measuring unit is used for etching the etched layer by adopting the etching process, measuring the variable quantity of the etching quantity of the etched layer along with time, and obtaining a curve graph of the etching speed of the etching process to the etched layer along with the change of the time;
the second measuring unit is used for etching the covering layer by adopting the etching process, measuring the variable quantity of the etching amount of the covering layer along with time, and obtaining a curve graph of the etching rate of the etching process to the covering layer along with the time;
and the obtaining unit is used for obtaining the ratio between the etching rate of the etched layer and the etching rate of the covering layer according to a curve graph of the etching process to the etched layer along with the change of time and a curve graph of the etching process to the covering layer along with the change of time, and the ratio is used as the etching selection ratio.
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| CN113067558A (en) * | 2021-03-03 | 2021-07-02 | 上海萍生微电子科技有限公司 | Diversified etching method for surface acoustic wave filter chip |
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| CN113067558A (en) * | 2021-03-03 | 2021-07-02 | 上海萍生微电子科技有限公司 | Diversified etching method for surface acoustic wave filter chip |
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